U.S. patent number 4,630,526 [Application Number 06/731,699] was granted by the patent office on 1986-12-23 for force control system including bypass flow path for implement with relatively movable frame parts.
This patent grant is currently assigned to Deere & Company. Invention is credited to Ronnie F. Burk, Larry M. Delfs, Michael R. Gilmore, Warren L. Thompson.
United States Patent |
4,630,526 |
Burk , et al. |
December 23, 1986 |
Force control system including bypass flow path for implement with
relatively movable frame parts
Abstract
A weight-balancing system for a farm implement, such as a disk
harrow with foldable wings operated by wingfold cylinders, includes
a selective control valve for controlling fluid communication to
the head and rod ends of the wingfold cylinders. A pair of
pressure-reducing/relieving valves permit individual adjustment of
the pressures in both the head and rod ends to achieve the desired
balance. In a preferred embodiment, a pilot-operated, two-position
valve is connected between the rod ends and one of the
pressure-responsive valves. The two-position valve is operated by
pressure signals generated by a flow-responsive switching valve
connected between the two-position valve and the selective control
valve. The switching valve and the two-position valve cooperate to
block the pressure-controlled outlet of the one pressure-responsive
valve and the rod ends and to bypass return fluid flow from the rod
ends to sump when the cylinders are being extended. Then, when
cylinder motion stops and this return flow ends, the switching
valve and the two-position valve are connected to the control
pressure outlet of the one pressure-responsive valve to the rod
ends to achieve the desired balance.
Inventors: |
Burk; Ronnie F. (Waterloo,
IA), Delfs; Larry M. (Cedar Falls, IA), Gilmore; Michael
R. (Davenport, IA), Thompson; Warren L. (Colona,
IL) |
Assignee: |
Deere & Company (Moline,
IL)
|
Family
ID: |
24940621 |
Appl.
No.: |
06/731,699 |
Filed: |
May 8, 1985 |
Current U.S.
Class: |
91/452; 91/518;
172/311 |
Current CPC
Class: |
A01B
63/14 (20130101); A01B 63/32 (20130101) |
Current International
Class: |
A01B
63/14 (20060101); A01B 63/32 (20060101); A01B
63/00 (20060101); F15B 013/06 (); B60G 011/30 ();
A01B 073/00 () |
Field of
Search: |
;172/311,316,328,413,456
;280/45B ;91/420,421,452,517,518 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Stouffer; Richard T.
Claims
We claim:
1. A force control system for an implement, the implement having a
first frame part, a second frame part movable with respect to the
first frame part, and at least one of the frame parts supporting a
ground-engaging tool, the control system comprising:
a hydraulic cylinder for connection between the frame parts to move
one frame part with respect to the other;
a pump;
a reservoir;
a control valve for controlling fluid communication between the
pump, the reservoir and head and rod ends of the cylinder, the
control valve having first and second outlet ports;
a pressure-controlling valve connected between one outlet port of
the control valve and one end of the cylinder; and
a bypass circuit communicated with the other outlet port and
comprising means for bypassing fluid flow around the
pressure-controlling valve from one end of the cylinder to the
control valve when the cylinder is moving in response to
pressurization of its other end, and comprising means for
communicating fluid pressure from the control valve to the one end
of the cylinder via the pressure-controlling valve when the
cylinder has reached a limit of its motion in response to
pressurization of its other end.
2. The force control system of claim 1, wherein:
the bypass circuit further comprises means for bypassing fluid flow
around the pressure-controlling valve from the control valve to the
one end of the cylinder when the control valve is operated to
pressurize the one end of the cylinder.
3. The force control system of claim 1, further comprising:
a further pressure-controlling valve connected between the control
valve and the other end of the cylinder.
4. The force control system of claim 3, wherein:
both pressure-controlling valves have high pressure inlets
communicated with the one outlet port of the control valve.
5. A force control system for an implement, the implement having a
first frame part, a second frame part movable with respect to the
first frame part, and at least one of the frame parts supporting a
ground-engaging tool, said control system including a hydraulic
cylinder for connection between the frame parts to move one frame
part with respect to the other, the control system further
including a pump, a reservoir, a control valve for controlling
fluid communication between the pump, reservoir, and first and
second ends of the cylinder and said control system also including
first and second pressure-controlling valves between the control
valve and the first and second ends, respectively, of the cylinder,
characterized by:
bypass means for providing a bypass flow path from the second end
of the cylinder to the reservoir when the first end of the cylinder
is pressurized via the first pressure-controlling valve, said
bypass flow path bypassing the second pressure-controlling valve,
and for directing pressurized fluid from the control valve to the
second cylinder end when the reservoir is communicated with the
first cylinder end via the firt pressure-controlling valve and via
the control valve.
6. The force control system of claim 5, wherein the bypass means
comprises:
a pressure-responsive valve having a first port communicated with
an outlet of the second pressure-controlling valve, a second port,
and a third port communicating with the second cylinder end and a
pressure-responsive valve member movable to a first position
wherein the second and third ports are in communication with each
other and wherein the first port is blocked and to a second
position wherein the first and third ports are communicated with
each other and wherein the second port is blocked.
7. The force control system of claim 6, further comprising:
a flow-responsive valve coupled between the pressure-responsive
valve and the control valve, the flow responsive valve forming a
portion of the bypass return flow path and comprising
flow-responsive means for generating a first pressure signal which
maintains the flow-responsive valve in its first position in
response to fluid flow through the bypass flow path and for
generating a second pressure signal which moves the flow-responsive
valve to its second position in response to an absence of fluid
flow through the bypass flow path.
8. The force control system of claim 7, wherein:
the pressure-responsive valve comprises a first fluid pilot for
moving the valve member to its first position;
a second fluid pilot for moving the valve member to its second
position; and
the flow-responsive valve comprising a first port communicated with
the control valve, a second port communicated with the second port
of the pressure responsive valve and with the first pilot of the
pressure-responsive valve, a third port communicated with the
second pilot of the pressure-responsive valve, and a valve member
movable to a first position wherein its first and second ports are
communicated with each other via a restriction so that fluid flow
across the restriction creates a pressure differential, the valve
member moving in response to this pressure differential to a second
position wherein its first and second ports are communicated with
each other and wherein the third port and the second pilot are
communicated with the reservoir via the first port and the control
valve, whereupon the first and second pilots operate to hold the
pressure-responsive valve in its first position, said valve member
moving in response to an absence of fluid flow across the
restriction to a third position wherein fluid communication between
the second pilot and the reservoir via the third port is locked,
whereupon the first and second pilots operate to move the
pressure-responsive valve to its second position.
9. The force control system of claim 8, wherein:
a pilot line connecting the outlet of the first
pressure-controlling valve to the second pilot of the
pressure-responsive valve, the pilot line having a restriction in
series with a check valve, the check valve permitting one way fluid
flow from the pressure-controlling valve to the second pilot of the
pressure-responsive valve.
10. The force control system of claim 5, wherein:
the first and second pressure-controlling valves are indentical,
each having a high pressure inlet communicated with the same outlet
of the control valve.
11. A wing force control system for an implement, the implement
having a frame for supporting ground-engaging tools, the frame
having a main section and at least one wing section pivotal with
respect to the main section, said control system including a
hydraulic cylinder for connection between the wing and the main
section to fold and unfold the wing, the control system further
including a pump, a reservoir, a control valve for controlling
fluid communication between the pump, reservoir, and the first and
second ends of the cylinder and said control system also including
first and second pressure-controlling valves between the control
valve and the first and second ends, respectively, of the cylinder,
characterized by:
bypass means for providing a bypass flow path from the second end
of the cylinder to the reservoir when the first end of the cylinder
is pressurized via the first pressure-controlling valve, said
bypass flow path bypassing the second pressure-controlling valve,
and for directing pressurized fluid from the control valve to the
second cylinder end when the reservoir is communicated with the
first cylinder end via the first pressure-controlling valve and via
the control valve.
Description
BACKGROUND OF THE INVENTION
This invention relates to a hydraulic system for controlling the
weight transfer between the main frame and wing sections of an
agricultural implement, such as a disk harrow.
One type of current disk harrow has a main frame and one or two
wings which are attached pivotally (or hinged) with respect to the
main frame. The main frame and the wings support gangs of disks
which are drawn through the soil. In such disk harrows, the
characteristic working or thrust force, due to implement-ground
interaction, can create functional problems as soil conditions
vary. These thrust forces act along the gang to create a moment
about the hinge centerline of the wing which tends to pull the wing
into the soil. Firm soils generate high thrust forces while loose
soils generate relatively low forces. As a result, in firm soils,
the wings may tend to penetrate deeper than the main frame while in
loose soils, the wings tend to ride out. The result is
unsatisfactory performance, i.e., ridging, incomplete cutout due to
lack of penetration, etc. The weight balance between the wings and
main frame is a delicate design parameter and is difficult to
optimize for different wing sizes and soil conditions. Oftentimes,
narrow wings tend to ride out and wide wings tend to penetrate too
deeply, or vice versa. Currently, these problems are addressed by
adding ballast to wing frames, by using compression springs in
wingfold cylinders, and by using additional gang wheels on large
wings. However, adjustment of ballast or of gauge wheels is
inconvenient so that it is difficult to quickly adjust to changing
soil conditions. Compression springs have a disadvantage in that
the force they provide varies, depending upon the relative position
between the main frame and the wing. Accordingly, some other more
convenient system for adjusting disk harrow weight balance is
desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a disk harrow,
weight transfer or ground-engaging force control system which is
simple to adjust.
Another object of the present invention is to provide disk harrow
main frame to wing weight transfer by controlling fluid pressure in
the wingfold cylinders.
A further object is to provide such a weight transfer system
wherein the weight transfer forces are independent of wing
position.
Another object is to provide a weight-balancing system in which
wing folding and unfolding can be controlled via a single lever and
with which the wingfold cylinders can be locked or floated.
Another object is to maintain constant weight transfer independent
of relative position of wing frame to main frame.
A further object of this invention is to provide such a system
using only a remote control valve such as a four-position, four-way
valve with float, such as typically used on agricultural
tractors.
These and other advantages are achieved by the present invention
wherein a pair of adjustable pressure-reducing/relieving valves are
included in the hydraulic circuit which controls the unfolding and
folding of the wings by extending and retracting hydraulic
cylinders. The hydraulic circuit includes a 4-position, 4-way
selective control valve connected to a pump and a reservoir. One
pressure-reducing/relieving valve is coupled between one outlet of
the control valve and the head ends of the wingfold cylinders. A
second pressure-reducing/relieving valve is connected between
another outlet of the control valve and the rod ends of the
cylinders. Thus, weight transfer can be achieved by individual
adjustment of the fluid pressures in the head and rod ends of the
wingfold cylinders.
A preferred embodiment also includes a pair of hydraulic wingfold
cylinders, a pump, a reservoir and a selective control valve for
controlling communication therebetween. A pair of
pressure-reducing/relieving valves separately control the pressures
in the head and rod ends of the cylinders. Both
pressure-reducing/relieving valves have high pressure inlets
connected to the same outlet port of the selective control valve.
The controlled pressure outlet of one pressure-reducing/relieving
valve is coupled directly to the head ends. The controlled pressure
outlet of the other pressure-reducing/relieving valve is coupled to
the rod ends via a two-position valve. A flow-responsive switching
valve generates pressure signals which operate the two-position
valve. During wing folding, (cylinder retraction), these valves
operate to pressurize the cylinder rod ends while connecting the
head ends to reservoir. The valves automatically shift from a wing
folding mode to an unfolding mode in response to shifting of the
selective control valve. During wing unfolding (cylinder
extension), the switching valve and the two-position valve operate
to bypass return fluid from the rod ends to sump without passing
through the other pressure-reducing/relieving valve and to block
communication between the rod ends and the controlled pressure
outlet of the other pressure-reducing/relieving valve. Then, when
the wings are unfolded and cylinder motion stops, the switching
valve and the two-position valve operate to automatically connect
the controlled pressure outlet of the other
pressure-reducing/relieving valve to the rod ends to achieve the
desired weight balancing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a conventional disk harrow with a main
frame, a pair of wings and a pair of wingfold hydraulic
cylinders.
FIG. 2 is a hydraulic circuit diagram of a weight transfer system
according to the present invention.
FIG. 3 is a hydraulic circuit diagram of a preferred embodiment of
the present invention.
DETAILED DESCRIPTION
Referring to FIG. 1, a conventional disk harrow 10 includes a
flexible 3-part frame 12 with a main section 14, and right and left
wing sections 16 and 18, respectively. A wing-folding function is
provided by wingfold hydraulic cylinders 20 and 22.
Referring now to FIG. 2, a hydraulic circuit 30 controls fluid flow
to and from the cylinders 20 and 22. Circuit 30 includes a pump 32,
a reservoir 34 and a 4-way, 4-position detent-held selective
control valve 36 which may be mechanically connected to a manually
operated control lever 38. Circuit 30 also includes
pressure-reducing/relieving valves 40 and 42 which may be
reducing/relieving valve model PPDB made by Sun Hydraulics. Lines
41 and 43 connect valve 36 to valves 40 and 42. Valve 40 controls
communication of lines 41 and 43 with the head end of cylinders 20
and 22 via line 44. Valve 42 controls communication of lines 41 and
43 with the rod ends of cylinders 20 and 22 via line 46.
Valve 36 includes an extend or unfold position 50, a shut-off
position 52, a retract or fold position 54 and a float position 55.
Valve 40 has opposed pressure-operated pilots 56 and 58 and is
spring-biased towards its illustrated position by manually
adjustable spring 60. Pilots 56 and 58 are connected to lines 43
and 44, respectively.
Valve 42 has opposed pressure-operated pilots 62 and 64 which are
connected to lines 41 and 46, respectively. Valve 42 is
spring-biased to its illustrated position by manually adjustable
spring 66.
When valve 36 is moved to the extend position 50, then line 41 is
connected to pump 32 and line 43 is connected to sump 34. Valve 40
communicates a reduced pressure (0-700 psi, determined by the
adjustment of manually adjustable spring 60) via line 44 to the
head ends of cylinders 20 and 22. At the same time, pump pressure
is communicated to pilot 62 of valve 42 while sump pressure is
communicated to pilot 64. Thus, valve 42 will connect the rod ends
of cylinders 20 and 22 to sump 36 and the cylinders will extend.
When the wings are unfolded and cylinder motion stops, then the
amount of downward wing force can be controlled by adjusting spring
60 of valve 40, which permits a pressure variation of 0 to 700 psi
for the pressure in the head ends of cylinders 20 and 22.
If, after the wings are unfolded, it is desired to reduce the
downward wing force by pressurizing the rod ends of cylinders 20
and 22, then control valve 36 should be shifted to and held in its
retract position 54. This pressurizes line 43 and connects sump 34
to line 41. With line 43 pressurized, valve 40 is held in the
position shown so that the head ends of cylinders 20 and 22 are
connected to sump. At the same time, pressure-reducing/relieving
valve 42 will pressurize line 46 and the rod ends of cylinders 20
and 22 to the pressure determined by pressure-adjust spring 66
(0-2500 psi).
To fold the wings or retract the cylinders, the pressure-adjusting
spring 66 on valve 42 must be adjusted to maximize the pressure in
line 46. Then, the control valve 36 is moved to position 54,
whereupon valve 42 connects pump 32 to the rod ends of the
cylinders 20 and 22 while valve 40 connects the head ends to sump
34. Thus, with hydraulic circuit 30, the wings 16 and 18 may be
folded or unfolded and the pressure in both the head and rod ends
of cylinders 20 and 22 may be adjusted.
Referring now to FIG. 3, the hydraulic circuit 170 controls the
cylinders 120 and 122. Circuit 170 includes a pump 132, a reservoir
134 and a 4-way, 4-position, detent held selective control valve
136 which may be mechanically connected to a manually-operated
control lever 138. Control valve 136 has a stop position 152, an
extend position 150, a retract position 154 and a float position
156. The hydraulic circuit 170 includes a pair of
pressure-reducing/relieving valves 172 and 174, such as
reducing/relieving valve model PPDB, made by Sun Hydraulics. Valves
172 and 174 are connected to one port of control valve 136 via line
141. Valve 172 is preferably factory adjusted so that the maximum
pressure in line 144 and in the head end of cylinders 120 and 122
is 750 psi, whereas valve 174 may be operator-adjusted to achieve a
desired rod end pressure. Both valves 172 and 174 are connected to
another port of control valve 136 via line 143.
Line 143 is also connected to port 175 of 3-position switching
valve 176. Valve 176 is spring-loaded to an intermediate position
178 by springs 180 and 182, and is urged to positions 184 and 186
by pressure-operated pilots 188 and 190, respectively. Valve 176
also has ports 192 and 194. Port 192 is connected to pilot 188 via
a restriction 189 and is connected to line 196. Pilot 190 is
connected to line 143 via a restriction 191. Port 194 is coupled to
line 195.
The circuit 170 also includes a two-position valve 200 with a port
202 connected to line 196, a port 204 connected to valve 174 via
line 206, and a port 208 which is coupled to the rod ends of
cylinders 120 and 122 via line 209. Valve 200 is urged towards a
position 210 by pilot 212 and towards position 214 by pilot 216 and
spring 218. Pilot 212 is connected to port 194 of switching valve
176 and to line 144 via restriction 220 and check valve 222. Pilot
216 is connected to line 196 via restriction 224.
Mode of Operation
Assuming that the cylinders 120 and 122 are retracted, (and the
wings folded), they may be extended by shifting valve 136 to
position 150, whereupon fluid flows from pump 132 to the head ends
of cylinders 120 and 122 via line 141, valve 172 and line 144. The
cylinders 120 and 122 extend and fluid flows out of the rod ends to
the reservoir 134 via line 209, valve 200 (position 214), valve 176
(position 178), line 143 and control valve 136. This creates a
pressure differential between ports 192 and 175 of valve 176 which
shifts valve 176 to position 184 wherein passage 185 vents line 195
to sump. This maintains low pressure at pilot 212 and keeps valve
200 in position 214, as illustrated. Restriction 220 is made small
enough to prevent pressurized fluid from bypassing the cylinders
120 and 122. Thus, the return fluid flow from the rod ends to sump
bypasses the pressure-reducing/relieving valve 174. Because of
this, pressure-reducing/relieving valve 174 can be set to any
desired setting and the resulting pressure in line 206 is blocked
by valve 200 so that this pressure does not reduce the force which
extends the cylinders when control valve 136 is initially in
position 150 and oil is flowing. The check valve 222 prevents fluid
flow from the rod ends back to the head ends if the control valve
136 is moved to position 152 before complete cylinder extension is
achieved so that the wings can be stopped in a partly unfolded
position.
When the wings are unfolded and the motion of cylinders 120 and 122
stops, the flow across valve 176 ends, thus removing the
differential pressure between ports 192 and 175, and valve 176
shifts back to its center position 178 wherein line 195 is blocked.
Then, the full 750 psi pressure from line 144 is applied to pilot
212 to shift valve 200 to position 210 wherein the rod ends of
cylinders 120 and 122 are connected to valve 174 via port 208, port
204 and line 206. At this point, the downward or upward force on
wings 16 and 18 is automatically adjusted according to the setting
of adjusting valve 174.
To retract cylinders 120 and 122 and fold the wings, valve 136 is
shifted to position 154 to pressurize line 143 and pilot 190. This
shifts valves 172 and 174 to the positions shown. It also shifts
valve 176 to position 186 and valve 200 to position 214, whereupon
fluid flows from pump 132 to the rod ends of cylinders 120 and 122
via valve 136, line 143, valve 176, line 196, valve 200 and line
209, thereby bypassing valve 174 so that full pump pressure is
available for wing folding. At the same time, fluid from the head
ends of cylinders 120 and 122 flows to sump via line 144, valve
172, line 141 and valve 136.
Thus, the pressure-reducing/relieving valve 174 (which controls
pressurization of the rod ends) can be preset to any desired
pressure. Then, during wing fold or unfold, this preset pressure
does not reduce the force tending to extend or retract the
cylinders, but when the wings are unfolded and cylinder motion
stops, this preset pressure is automatically applied to the rod
ends to oppose the head end pressure from
pressure-reducing/relieving valve 172, thus automatically achieving
the desired wing force or weight balance.
In the stop position 152 of valve 136, both lines 141 and 143 are
blocked. Valve 200 assumes position 214 communicating line 209 with
blocked line 143. Valve 172 assumes the position shown and
communicates line 144 with blocked line 141. As a result, flow is
blocked in lines 144 and 209 and the cylinders 120 and 122 are
immobilized. This stop mode is needed to halt motion during a
folding or unfolding cycle, such as to prevent a wing from striking
an obstruction.
In the float position 156 of valve 136, lines 141 and 143 are both
connected to reservoir 134. Valves 172, 176 and 200 assume the same
positions which they assume in the stop mode so that lines 144 and
209 are both communicated with each other and with the reservoir.
This allows free motion of the cylinders 120 and 122. This float
mode is useful in the case of a system malfunction or in the case
where the disk is operated in soil where no weight transfer is
needed.
In addition to weight balancing, this invention has other
applications in the agricultural implement area. One such
application would be disk harrow front-to-rear leveling.
Front-to-rear leveling is used to control the relative disking
depth of the front and rear gangs. Disk leveling is important to
ensure uniform soil cutout and to maintain a level soil surface
across the width of the machine. Some current level action disks
use a mechanical linkage to control front-to-rear leveling. The
linkage utilizes the relative position of the hitch to the main
frame to control the compression of the leveling spring which, when
relaxed, lets the front gangs penetrate deeper and, when
compressed, pulls the front gangs out of the soil. The same effect
could be realized if the leveling linkage were removed, a hydraulic
cylinder installed between the hitch and main frame and the present
balancing system installed to control the position of the cylinder.
The system could be set to obtain a level disking job and the same
front-to-rear disking depth would be maintained, regardless of the
relative position of the hitch to the main frame (disking over
small knolls or through low spots.)
Another application would be for planting unit down force control.
Current planting units utilize two extension springs to create a
down force to help keep the unit in the soil. This force is not
constant and decreases as the planting unit flexes down. The
present balancing system would be connected to a hydraulic cylinder
which would replace the springs to provide a constant force on the
unit. Such a system would also be adjustable to compensate for
varying soil conditions.
While the invention has been described in conjuction with a
specific embodiment, it is to be understood that many alternatives,
modifications and variations will be apparent to those skilled in
the art in light of the aforegoing description. Accordingly, this
invention is intended to embrace all such alternatives,
modifications and variations which fall within the spirit and scope
of the appended claims.
* * * * *